Power semiconductor switches such as IGBTs (insulated gate bipolar transistors) or MOSFETs are used nowadays in a multitude of applications, for example in converter circuits. Independently of the specific use of a power semiconductor switch, a robust behavior in the case of short circuits is often desired. In the case of a short-circuited load, a switched-on power semiconductor switch is in the short-circuit operating mode, i.e., a high short-circuit current flows through the power semiconductor switch while at the same time a high voltage drop (usually equal to the intermediate circuit voltage in the case of a converter) across the load current path of the power semiconductor switch. The consequence is a very high power loss in the power semiconductor switch and correspondingly high heating above a critical temperature, which results in thermal runaway and thus the destruction of the power semiconductor switch.
In order to prevent destruction of the power semiconductor switch in the short-circuit operating mode (or generally in an overload operating mode), the power semiconductor switch has to be turned off after a specific time (e.g., 10 μs), in order that the energy (short-circuit current times operating voltage times time) dissipated during the overload operating mode remains below a critical value, wherein this critical energy is dependent on the specific construction of the power semiconductor switch. In order to prevent thermal runaway, the power semiconductor switch can be driven such that the short-circuit current does not exceed a defined maximum value and, consequently, the critical energy is not exceeded up to the turn-off of the power semiconductor switch. However, this can adversely affect the performance (e.g., with regard to the losses in the switched-on state) in the normal operating mode of the power semiconductor switch.